litex/soc/cores/prbs.py

   1 # This file is Copyright (c) 2015-2019 Florent Kermarrec <florent@enjoy-digital.fr>
   2 # This file is Copyright (c) 2015 Sebastien Bourdeauducq <sb@m-labs.hk>
   3 # License: BSD
   4
   5 from operator import xor, add
   6 from functools import reduce
   7
   8 from migen import *
   9 from migen.genlib.cdc import MultiReg
  10
  11 # PRBS Generators ----------------------------------------------------------------------------------
  12
  13 class PRBSGenerator(Module):
  14     def __init__(self, n_out, n_state=23, taps=[17, 22]):
  15         self.o = Signal(n_out)
  16
  17         # # #
  18
  19         state = Signal(n_state, reset=1)
  20         curval = [state[i] for i in range(n_state)]
  21         curval += [0]*(n_out - n_state)
  22         for i in range(n_out):
  23             nv = reduce(xor, [curval[tap] for tap in taps])
  24             curval.insert(0, nv)
  25             curval.pop()
  26
  27         self.sync += [
  28             state.eq(Cat(*curval[:n_state])),
  29             self.o.eq(Cat(*curval))
  30         ]
  31
  32
  33 class PRBS7Generator(PRBSGenerator):
  34     def __init__(self, n_out):
  35         PRBSGenerator.__init__(self, n_out, n_state=7, taps=[5, 6])
  36
  37
  38 class PRBS15Generator(PRBSGenerator):
  39     def __init__(self, n_out):
  40         PRBSGenerator.__init__(self, n_out, n_state=15, taps=[13, 14])
  41
  42
  43 class PRBS31Generator(PRBSGenerator):
  44     def __init__(self, n_out):
  45         PRBSGenerator.__init__(self, n_out, n_state=31, taps=[27, 30])
  46
  47 # PRBS TX ------------------------------------------------------------------------------------------
  48
  49 class PRBSTX(Module):
  50     def __init__(self, width, reverse=False):
  51         self.config = Signal(2)
  52         self.i = Signal(width)
  53         self.o = Signal(width)
  54
  55         # # #
  56
  57         config = Signal(2)
  58
  59         # generators
  60         self.specials += MultiReg(self.config, config)
  61         prbs7 = PRBS7Generator(width)
  62         prbs15 = PRBS15Generator(width)
  63         prbs31 = PRBS31Generator(width)
  64         self.submodules += prbs7, prbs15, prbs31
  65
  66         # select
  67         prbs_data = Signal(width)
  68         self.comb += \
  69             If(config == 0b11,
  70                 prbs_data.eq(prbs31.o)
  71             ).Elif(config == 0b10,
  72                 prbs_data.eq(prbs15.o)
  73             ).Else(
  74                 prbs_data.eq(prbs7.o)
  75             )
  76
  77         # optional bits reversing
  78         if reverse:
  79             new_prbs_data = Signal(width)
  80             self.comb += new_prbs_data.eq(prbs_data[::-1])
  81             prbs_data = new_prbs_data
  82
  83         # prbs / data mux
  84         self.comb += \
  85             If(config == 0,
  86                 self.o.eq(self.i)
  87             ).Else(
  88                 self.o.eq(prbs_data)
  89             )
  90
  91 # PRBS Checkers ------------------------------------------------------------------------------------
  92
  93 class PRBSChecker(Module):
  94     def __init__(self, n_in, n_state=23, taps=[17, 22]):
  95         self.i = Signal(n_in)
  96         self.errors = Signal(n_in)
  97
  98         # # #
  99
 100         state = Signal(n_state, reset=1)
 101         curval = [state[i] for i in range(n_state)]
 102         for i in reversed(range(n_in)):
 103             correctv = reduce(xor, [curval[tap] for tap in taps])
 104             self.sync += self.errors[i].eq(self.i[i] != correctv)
 105             curval.insert(0, self.i[i])
 106             curval.pop()
 107
 108         self.sync += state.eq(Cat(*curval[:n_state]))
 109
 110
 111 class PRBS7Checker(PRBSChecker):
 112     def __init__(self, n_out):
 113         PRBSChecker.__init__(self, n_out, n_state=7, taps=[5, 6])
 114
 115
 116 class PRBS15Checker(PRBSChecker):
 117     def __init__(self, n_out):
 118         PRBSChecker.__init__(self, n_out, n_state=15, taps=[13, 14])
 119
 120
 121 class PRBS31Checker(PRBSChecker):
 122     def __init__(self, n_out):
 123         PRBSChecker.__init__(self, n_out, n_state=31, taps=[27, 30])
 124
 125 # PRBS RX ------------------------------------------------------------------------------------------
 126
 127 class PRBSRX(Module):
 128     def __init__(self, width, reverse=False):
 129         self.i = Signal(width)
 130         self.config = Signal(2)
 131         self.errors = Signal(32)
 132
 133         # # #
 134
 135         config = Signal(2)
 136
 137         # optional bits reversing
 138         prbs_data = self.i
 139         if reverse:
 140             new_prbs_data = Signal(width)
 141             self.comb += new_prbs_data.eq(prbs_data[::-1])
 142             prbs_data = new_prbs_data
 143
 144         # checkers
 145         self.specials += MultiReg(self.config, config)
 146         prbs7 = PRBS7Checker(width)
 147         prbs15 = PRBS15Checker(width)
 148         prbs31 = PRBS31Checker(width)
 149         self.submodules += prbs7, prbs15, prbs31
 150         self.comb += [
 151             prbs7.i.eq(prbs_data),
 152             prbs15.i.eq(prbs_data),
 153             prbs31.i.eq(prbs_data)
 154         ]
 155
 156         # errors count
 157         self.sync += \
 158             If(config == 0,
 159                 self.errors.eq(0)
 160             ).Elif(self.errors != (2**32-1),
 161                 If(config == 0b01,
 162                     self.errors.eq(self.errors + (prbs7.errors != 0))
 163                 ).Elif(config == 0b10,
 164                     self.errors.eq(self.errors + (prbs15.errors != 0))
 165                 ).Elif(config == 0b11,
 166                     self.errors.eq(self.errors + (prbs31.errors != 0))
 167                 )
 168             )